Time-of-Use Electricity Calculator
Compare a flat electricity rate against a time-of-use plan using your peak, shoulder, and off-peak rates, monthly kWh allocation, fixed charge, and optional EV or night charging shift.
Reviewed May 26, 2026. JouleIO calculators are planning tools; confirm final utility rates, equipment specs, incentives, installation bids, and safety decisions with official utility, manufacturer, installer, DOE, ENERGY STAR, EPA, IRS, or EIA sources.
1. Enter real usage
Use your actual watts, runtime, home size, miles, battery size, or appliance schedule.
2. Localize the rate
Compare national assumptions with your state, utility bill, time-of-use plan, or project quote.
3. Verify before acting
Check final prices, rebates, tax rules, and safety requirements before buying or installing equipment.
EIA state averages are flat-rate planning baselines, not utility TOU tariffs. Enter TOU prices from the exact rate schedule you are comparing.
U.S. EIA 2026-02
Customer charge or minimum monthly fee applied to both plans.
900
Sum of peak, shoulder, and off-peak usage.
TOU Rates and kWh Allocation
Enter the energy used in each rate period. If your utility only has peak and off-peak periods, set shoulder kWh and shoulder rate to zero.
25% of entered usage
35% of entered usage
40% of entered usage
Often late afternoon or evening.
Mid-peak or partial-peak period.
Usually overnight or low-demand hours.
Optional EV / Night Charging Shift
Model flexible kWh moved into off-peak hours without changing total monthly consumption.
Applied shift: 180 kWh/month.
The calculator caps the shift at available kWh in that source period.
Off-peak period
Use this for EV charging, pool pump timers, laundry, dishwasher, or water heating.
Flat Bill
per month at 17.65¢/kWh
TOU After Shift
blended 14.95¢/kWh before fixed charge
Annual Difference
TOU scenario compared with flat-rate bill.
Bill Comparison
| Scenario | Energy Cost | Fixed Charge | Monthly Bill | Annual vs Flat |
|---|---|---|---|---|
| Flat rate | $158.85 | $15.00 | $173.85 | $0 baseline |
| TOU before shift | $175.95 | $15.00 | $190.95 | $205 higher |
| TOU after shift | $134.55 | $15.00 | $149.55 | $292 saved |
Load-shift value
$497/yr
Savings from moving 180 kWh/month to off-peak.
TOU blended rate
14.95¢/kWh
Before shift: 19.55¢/kWh.
After-shift kWh
Peak 45 kWh, shoulder 315 kWh, off-peak 540 kWh.
Transparent Assumptions
Included
Monthly kWh in each TOU period, user-entered TOU energy rates, flat-rate baseline, fixed monthly charge, and optional load shifting into off-peak hours.
Not included
Utility eligibility, address-specific tariff rules, taxes, riders, demand charges, minimum bills, solar export credits, seasonal calendars, holidays, or enrollment fees.
Best input source
Use interval data from your utility portal when available. Otherwise, test several peak/off-peak splits before changing rate plans.
Next step
If TOU wins, compare the same assumptions in the electricity bill calculator and model EV charging separately in the EV charging calculator.
When a TOU Plan Beats a Flat Rate
A time-of-use plan is favorable when enough usage lands in cheaper periods to offset the higher peak price. The important number is the blended TOU rate: total TOU energy cost divided by total kWh. If that blended rate is lower than your flat rate after realistic scheduling, TOU can reduce your bill. If evening HVAC, cooking, and household activity dominate your usage, the same TOU plan can cost more.
Good Loads to Shift Off-Peak
EV charging
Use vehicle or charger scheduling so charging starts after the off-peak window begins.
Laundry and dishwasher
Use delay-start features when noise, safety, and household routine allow.
Pool pumps
Move filtration hours away from peak periods while still meeting water-quality needs.
Water heating
Use timers or controls only when the heater and household demand can support it.
Frequently Asked Questions
How do I compare a flat rate with a time-of-use electricity plan?
Use the same monthly kWh for both plans. The flat bill is total kWh multiplied by the flat rate, plus fixed charges. The TOU bill splits the same kWh across peak, shoulder, and off-peak periods, multiplies each bucket by its rate, and adds the same fixed charges. The difference shows whether the TOU plan is cheaper or more expensive for your usage pattern.
Where do I find peak, shoulder, and off-peak kWh?
The best source is your utility account portal if it provides hourly or 15-minute interval usage. Map each interval to the rate periods in the tariff. If you only have a monthly bill, start with an estimate, then test sensitivity by moving more evening usage into peak or more flexible usage into off-peak.
Does this calculator know whether my utility offers a TOU plan?
No. JouleIO does not claim address-level utility eligibility. Enter rates from the specific tariff you are considering and confirm plan availability, season definitions, holidays, minimum bills, riders, and enrollment rules with your utility before switching.
How does EV or night charging shift affect TOU savings?
Flexible charging moves kWh from a higher-price period to off-peak. The value is roughly shifted kWh multiplied by the price spread between the original period and the off-peak period. EV charging, pool pumps, dishwashers, laundry, and water-heater timers are common flexible loads, but comfort and equipment limits still matter.
What costs are excluded from this TOU comparison?
This calculator compares energy charges plus one monthly fixed charge. It does not automatically include taxes, riders, demand charges, tiered thresholds, minimum bills, seasonal TOU calendars, net metering, export credits, solar billing rules, or one-time enrollment costs.